A new compound methyleneaminonitroguanidine (MANG) was synthesized using aminoguanidine （ANQ）and formaldehyde as raw materials, and the reaction process was analyzed. The crystal structure of MANG was analyzed by an X-ray single diffractometer. Results show that the crystal belongs to an orthorhombic crystal system. Its space group is P_nn2. Each unit cell contains four MANG molecules, and the crystal density is 1.63 g·cm^-3. Thermal behaviors of MANG were studied by differential scanning calorimetry(DSC) and thermogravimetry-derivative thermogravimetry (TG-DTG). MANG presents only one intense exothermic decomposition process. At a heating rate of 5 ℃·min^-1, the decomposition peak temperature and exothermic quantity of MANG are 170.9 ℃ and 1440 J·g^-1, respectively. The standard molar enthalpy of combustion and the standard molar enthalpy of formation of MANG obtained by calculation are -1526.09 kJ·mol^-1 and 33.81 kJ·mol^-1, respectively. The detonation velocity 7.1 km·s^-1 and detonation pressure 20.9 GPa of MANG predicted by Kamlet-Jacobs(K-J) equation are less than those of ANQ, but higher than those of TNT. The impact sensitivity(>7.9 J) of MANG is lower than that of ANQ(3 J) and RDX(7.4 J).